PHP Design Patterns: Frequently Asked Questions

PHP design patterns are mainly used to solve common programming problems, including the following solutions: Observer pattern: achieve loose coupling by separating objects and events. Singleton pattern: Ensure that a class has only one instance. Strategy mode: achieve scalability through exchange algorithm.

PHP Design Patterns: FAQ

Introduction

Design patterns are Reusable software solutions for common programming problems. They provide a modular and structured way to organize and write code. In PHP, there are several design patterns that can be used to solve various problems.

Common problems and their design pattern solutions

1. How to avoid tight coupling?

• Observer pattern: Separate objects through events and listeners to achieve loose coupling.

//创建一个观察者
class Logger implements Observer {

    public function update(Subject $subject) {
        echo $subject->getState() . PHP_EOL;
    }
}

//创建一个主题
class User {

    private $observers = [];

    public function attach(Observer $observer) {
        $this->observers[] = $observer;
    }

    public function notify() {
        foreach ($this->observers as $observer) {
            $observer->update($this);
        }
    }

    public function changeState($state) {
        $this->state = $state;
        $this->notify();
    }
}

//创建一个会话
$user = new User();

//创建一个记录器观察者
$logger = new Logger();

//将记录器观察者附加到用户
$user->attach($logger);

//更改用户状态并触发通知
$user->changeState('Logged in');

2. How to implement singleton mode?

• Singleton pattern: Ensure that a class has only one instance and provide a way to globally access that instance.

class Database {

    private static $instance = null;

    private function __construct() {}

    public static function getInstance() {
        if (self::$instance === null) {
            self::$instance = new self();
        }

        return self::$instance;
    }
}

//使用单例
$db = Database::getInstance();

3. How to create scalable code?

• Strategy Mode: Allows swapping algorithms, thus enabling scalability.

interface SortStrategy {

    public function sort(array $data);
}

class BubbleSortStrategy implements SortStrategy {

    public function sort(array $data) {
        //冒泡排序算法
    }
}

class InsertionSortStrategy implements SortStrategy {

    public function sort(array $data) {
        //插入排序算法
    }
}

class Sorter {

    private $strategy;

    public function setStrategy(SortStrategy $strategy) {
        $this->strategy = $strategy;
    }

    public function sort(array $data) {
        $this->strategy->sort($data);
    }
}

//使用策略图案
$sorter = new Sorter();
$sorter->setStrategy(new BubbleSortStrategy());
$sorter->sort([1, 3, 2, 4]);

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